Usage patterns
〈人〉はせっかちだto describe someone as impatient/hasty
He's impatient and always rushes other people.
せっかちな性格an impatient personality
Because of his impatient personality, he often makes mistakes from not double-checking things.
せっかちに〈動詞〉to do something hastily/impatiently
It's better not to jump to conclusions hastily.